Modification of starch



Patented Apr. 4, 1950 MODIFICATION OF STAROH Ralph Waldo Kerr,Riverside, Ill., asllgnor to Corn Products Refining Company, New York.N. Y., a corporation of New Jersey No Drawing. Application December 13,1945, Serial No. 634,890

25 Claims. (Cl. 127-38) This invention relates to the manufacture ofmodified starch products such as thin boiling starches, pyrodextrins,gums, and the like.

An object of the invention is to provide an improved process for themanufacture of such products. A further object or the invention is toprovide such products having improved characteristics.

Heretofore thin boiling starches, dextrins and the like have been madeby long and complicated procedures. The most common procedures formaking thin boiling starches involve heating an acidified starch slurryat temperatures of'about 125 F. for periods of 8 to 24 hours.Thereafter, the slurry is neutralized and filtered. The treated starchis then washed and dried. In some cases, if starch having a rather highfluidity value is desired, the starch slurry may be filtered withoutbeing neutralized and the moist cake may be dried and heated in a warmkiln for several days.

The common methods for the preparation of pyrodextrins, gu s and thelike involve roasting starches of low moisture content in the presenceof atomized acid. The temperatures may be as 1 ducing thin boilingstarches, pyrodextrins and 90 the like having improved properties whichmethod obviates the difiiculties of former methods. The process of myinvention is simple and requires comparatively little time.

In general the process of my invention ema braces treating starch withsmall amounts of aluminum chloride hexahydrate under controlledconditions of moisture and temperature. The term aluminum chloride asused hereinafter is intended to mean aluminum chloride hexahydrate. do

I am aware that it has been proposed heretofore to use aluminum chlorideas a starch modifying agent and that more generally it has been proposedto use as starch modifying agents those 2 in any event, at a temperaturepreferably insuflicient to eflect gelatinization or the starch, stir theslurry well and then filter the same. I1 aluminum chloride is added to astarch slurry having a density between 17 B6. and 22 B. which range hasbeen found to cover practical operating conditions, the amount of suchsalt retained by the starch after filtration is about per cent 01' thealuminum chloride originally added. The filtrate, obtained from one suchfiltering operation, with appropriate additions of aluminum chloride tocompensate for the amount retained by the filtered starch may be usedadvantageously for starch to be treated subsequently.

Another method of adding aluminum chloride to starch is simply to addaluminum chloride in dry form to dry starch and thereafter to mixthoroughly the two materials. A third method is to dissolve aluminumchloride in an alcoholic solution, add the solution to dry starch withthorough mixing, and then remove the alcohol. In fact any desired methodmay be used for admixing aluminum chloride with starch which tends toinsure that the aluminum chloride will be evenly distributed throughoutthe starch.

The second step of carrying out the present invention involves heatingthe starch to which aluminum chloride has been added. This may beeflected in several ways. The simplest method is to carry out thedesired modification of the starch in a commercial type of air drierthrough which heated air is circulated. Alternatively the starch may betreated in such a drier to effect partial modification thereof and thebalance of the treatment may be carried out by roasting at a highertemperature in a dextrin cooker or the like. A third method of heattreating starch in the presence of aluminum chloride is to pass a slurryof starch containing aluminum chloride over heated rolls in the mannergenerally disclosed in-U. S. Patent No. 1,979,257, issued November 6,1934. Alternatively, the slurry may be filtered on a mechanical filterand the filter cake passed over such rolls.

metallic salts which are adapted to decompose 4 When a slurry of starchadmixed with alumiwith the resultant formation of free acid. Patentsdirected to the use of such materials are as follows: U. S. 536,260,issued March 26, 1895, to Bloede; U. S. 610,182, issued September 6,1898,

to Higgins; and U. S. 1,284,495, issued November 50 12, 1918, toTunnell. However, as will appear more fully from the followingdescription, the present invention contemplates marked and sub-'stantial departures from practices heretofore known.

In carrying out my invention aluminum chloride is first added to starch.This addition may be affected in several ways. The simplest and mosteffective method is to add aluminum chloride to a starch slurry at roomtemperature. or, well as the heating of the latter in the presence numchloride in amounts hereinafter specified is heated above thegelatlnization temperature of the starch, it is observed that the starchis gelatinized but is not noticeably modified by the aluminum chloridepresent. Accordingly this meth- .od of heating is' ineffective forpurposes of the the absence of undue amounts of free water.

On the other hand, as above indicated, slurries containing starch andaluminum chloride can be utilized in practicing the present invention ifsuch slurries are passed over heated rolls or the like which permitrapid drying of the starch as of aluminum chloride. It is believed thatthe driving oi! of excess moisture is a necessary preliminary to thedesired modification of the starch under treatment on the rolls.

Other methods of heat treating starch in the presence of aluminumchloride include combinations of these various methods previouslyindicated. In fact, any means of heating may be used provided conditionsare controlled as will be specified hereinafter.

After the heat treatment is completed, it is generally desirable toadjust the pH value of the starch which has undergone treatment to about5.0 to 6.0 preferably with gaseous ammonia. This range of pH valuesappears desirable for most applications of the products obtainedaccording to the present invention. Other volatile bases, such asethylamine, may also be used to adjust the pH values of starch aftertreatment as above indicated. Bases, such as sodium hydroxide, may

also be used if there is no objection to the presence of ash formed bytheir addition. The adjustment of the pH value as above indicated alsoserves to arrest the action of aluminum chloride upon the starch.

The use of aluminum chloride in treating starches in accordance with myinvention may be extended to produce practically all of the common typesof modified starches, including thin boiling starches, gums, dextrins,pregelatinized cold water soluble starches and drum dried dextrins buthaving the improved properties heretofore mentioned. To produce productsof these various types, however, the conditions employed in carrying outthe process of the invention will vary, as will appear more fullyhereinafter.

In obtaining products of these various types, the conditions under whichthe desired modification and also the extent of the modification ofstarch with aluminum chloride is effected in accordance with the presentinvention depend upon several factors or variables. These factors aremore or less interrelated. They are (1) the amount of aluminum chloride,(2) the .pH value of starch undergoing treatment, (3) moisture contentof starch during treatment, (4) temperature of the starch duringtreatment, and.(5) time of treatment.

The amount of aluminum chloride which is necessary to produce thedesired effect upon starch in practicing my invention is very small, 1.e., of the order of about 0.05 percent, based upon the dry weight of thestarch. Amounts of the salt larger than this may also be used but theamount should not exceed about 0.4 to about 0.5 percent of aluminumchloride, based upon. the dry weight of the starch. Within the indicatedlimits, the greater the amount of aluminum chloride, the greater will bethe extent of the modification of starch, other factors being constant.If amounts of aluminum chloride larger than about 0.5 percent are used,there will be difficulty in controlling the reaction and also inobtaining the desired products.

The pH value of starch, as that term is hereinafter defined, to betreated in accordance with the present invention, should be within therange of about 2.8 to about 3.4 and preferably within the range of about8.0 to about 3.4. In view of the property of aluminum chloride to formalu minum hydroxide and an aluminate with alkaline solutions, it ispreferable not to use water, for slurrying the starch, having a pH valuehigher than 7.0. However, should the pH value of the starch in waterslurry be higher than 3. adjust= ment of the pH value may be made byadding to the starch slurry a suitable acid, such as hydrochloric acid.If the starch supplied for use in carrying out the invention containsabnormally high amounts of sulfur dioxide (or other similar volatileacids), then a pH value of the starch slurry in the range of about 2.8to 3.0 is quite permissible since the sulfur dioxide will be volatilizedduring subsequent heat treatment. Should the pH value he too low, it maybe adjusted with a suitable alkaline agent, such as ammonium hydroxide,sodium carbonate and the like. For practical operations, so calledcondensate water from evaporators, boilers, etc., is satisfactory forwashing the starch preliminarily and for slurrying starch to produceadmixtures of starch and aluminum chloride as hereinabove described.

The moisture content of starch which is to be treated in accordance withthe present invention, 1. e., the amount of moisture present with thestarch, may va over a wide range but, in any case, will depend upon thetemperature employed during the heat treatment and upon the type ofproduct desired. The effect of aluminum chloride on starch is greatestwhen small amounts of moisture are present with the starch and leastwhen large amounts of moisture are present with the starch, otherfactors being constant. Therefore, it is advantageous to provide for theremoval of moisture during the heat treatment and/or to use starchhaving a rather low initial moisture content.

In some instances, as in the production of thin boiling starches,dextrins or the like from starch in accordance with the presentinvention, gelatinization is to be avoided and in such cases themoisture content of the starch undergoing treatment should bepredetermined, so that at any given temperature employed during themodification treatment there is insufiicient moisture present to permitgelatinization to any appreciable degree. If predetermination of themoisture content of the starch is not feasible or desired, comparableresults may be obtained through careful control of the temperature whichshould not exceed that at which gelatinization occurs until, as throughheating, the moisture content of the starch is reduced sufiiciently sothat gelatinization will not occur if the temperature should be raisedabove the gelatinization temperature of the starch.

Whether the temperatures employed in effecting the modifications of thepresent invention are above or below the gelatinization temperature, andwhether the starch to be modified is gelatinized or ungelatinized, thedesired modification of starch in the presence of aluminum chlorideproceeds more effectively in the presence of relatively small amounts ofmoisture than in the presence of relatively large amounts of moisture.The moisture content of starch undergoing modification in accordancewith the invention should generally be within the rangeof about 1 to 2percent to about 30 percent, and preferably within the range of about 1to 2 percent to about 20 percent, based upon the total weight of thestarch and moisture. It is to be understood, however, that starchinitially containing, or in the presence of, larger amounts of moisturethan above specified may be heated with aluminum chloride with a view toobtaining the products contemplated by the present invention, but thatthe starch modification with which the present invention is concernedwill not become manifest unless and until excess moisture has beenreture content of the starch should be reduced below about 20 percent. Amoisture value of about 9 to 12 percent is a practical operating valuefor making thin boiling starches in accordance with the presentinvention, when the temperature of the starch is of the order of about75 C. to about 95 C.

In making dextrins, where again gelatinization is to be avoided,somewhat lower moisture co'ntents than those above specified arepreferable, although the same considerations as to moisture content andtemperature apply. A moisture value of about 5 to 7 percent is apractical operating value for making dextrins in accordance with thepresent invention, when the temperature of the starch is of the order ofabout 90 C. to about 105 C.

In making gelatinized starch products according to the present inventionby means of heated rolls, higher moisture values, i. e., about 45percent to about 60 percent or even higher are generally satisfactorysince the moisture content is immediately reduced by the heat of therolls.

The temperature of the starch during the modification thereof withaluminum chloride may vary from about C. to about 105 C. provided themoisture values are controlled as above indicated. The reaction at roomtemperature, however, proceeds extremely slowly and is not practicable.At temperatures above 105 C. it is difllcult to prevent charring of thestarch and to control the reaction.

The time of the heat treatment required to obtain the desired productswill depend upon the amount of aluminum chloride, the moisture contentof the starch and the temperature of the starch undergoing treatment.The larger the amount of aluminum chloride, the lower the moisturecontent of the starch, and the higher the temperature of the starchduring treatment, the shorter will be the time required for thetreatment. The shortest period of time is a matter of a few seconds whenthe starch is subjected to treatment over rolls. Thin boiling starchesand dextrins may be prepared within about to 45 minutes. Ordinarily thetime [101' treatment does not exceed about 2 to 3 hours.

Due to the large number of combinations of concentration of aluminumchloride, moisture content, temperature and time factors possible underthe present invention and the wide variety of products which it ispossible to produce in accordance therewith, it is not feasible toattempt to set forth the exact operating conditions for each productpossible of production. Below are presented some tables which will showthe effect of-each of these factors, the other factors being constant.Persons skilled in the art will have no dimculty in determining throughsuitable preq liminary tests which particular conditions of treatmentare best suited to obtain the products they desire.

In thatportion of the description which follows reference will be had toseveral definitive expressions, analytical methods and the like. Theexplanation which follows at this point is intended to render clear themeaning of such expressions and methods.

pH value of starch-In describing and claiming the present invention thisexpression has referencev to admixtures of starch and aluminum chloride.The value is determined as follows:

An admixture of starch and aluminum chloride under test is slurried indistilled water to iorm a slurry having a density of 10 B. at

1''. This slurry is shaken for 30 minutes and then centrifuged. The pHvalue of the separated liquor is then measured in conventional manner.

In the case of comparative Tables VII, VIII and IX where hydrochloricacid is used, however, the expression pH value of starch refers to thedetermination made by the described procedure except that hydrochloricacid is substituted for aluminum chloride.

Solution viscosity test.-Into 20 or 30 milliliters of 2 normal potassiumhydroxide in a ml. beaker is stirred 0.2500 gram of starch (drysubstance). The mixture is stirred for several minutes and .is thenallowed to stand overnight at room temperature. Then the solution istransferred quantitatively to a 50 ml. volumetric flask and the solutionis made up to 50 ml. volume with 2 N potassium hydroxide.

The solution is transferred to an Ostwald viscometer (capacity about 6ml.), fi1ling the latter to the lower mark. The viscometer is placed ina water bath having a temperature of 25 C.

10.05% After about 15 minutes, suction is applied in order to draw thesolution up to the higher mark. The number of seconds is then noted forthe meniscus to reach the lower mark on the viscometer.

A similar viscosity determination is made on the 2 N potassium hydroxidewhich is used as the solvent for the starch.

The specific viscosity at a concentration of 0.5 g. per 100 cc. (am) iscalculated as follows:

viscosity of solution in seconds-viscosity of solvent viscosity ofsolvent Specific viscosities determined by means of the above formulaand method will be found to vary for different samples of material undertest in much the same way as do the more conventional v determinationsof fluidity, and Scott or hot paste viscosity. The specific viscosity isin fact a linear function of the conventional fluidity values. For thinboiling starches prepared in accordance with the present invention, thefollowing results were obtained and correlated against the Scott test(for hot paste viscosity) and fluidity. The sam- Soluble material.Thepercentage of soluble material in starch is determined as follows:

A one gram sample of the material is made up to 100 ml. with water. Themixture is then weight of residue X 2 weight of sample X 100Ferricyzmide number.--This is an index to the reducing value of sugarsand the like and is determined as set out below following the method asdescribed by Gore and Steele, Ind. Eng. Chem., Anal. Ed., 7, 324 (1935).

Two hundred anf fifty milligrams of starch is dissolvedin 25 ml. ofboiling water and heated in a boiling water bath for 2 minutes. 25 ml.of alkaline ferricyanide reagent is added and the mixture held in theboiling water bath for an additional minutes. It is then cooled quicklyto 25 C., whereupon 60 ml. of zinc sulfate-acetic acid reagent and ml.of 20% potassium iodide solution are added. The liberated iodine istitrated with 0.05 normal thiosulfate. The ferricyanide number isexpressed as the ml. of 0.1 normal ferricyanide consumed per gram ofmaterial (dry substance basis).

Linear polymers determination.-The percentage of linear polymercomponents in starch is determined spectrophotometrically withiodinestained solutions according to the method of Kerr and Trubell,Paper Trade Journal, 117, No. 15, (1943).

Fluidity vaZue.This is determined in accordance with the methoddescribed in Chemistry and Industry of Starch, Kerr (1944) rp. 95.

Stormer test.This is determined in accordance with the proceduredescribed in Chemistry and Industry of Starch, supra, p. 88.

Gel strength-This is determined in accordance with the Saare disc methoddescribed in Chemistry and Industry of Starch, supra, p. 97.

Scott test.--This test is carried out in accordance with the proceduredescribed in "Chemistry and Industry of starch, supra, pp. 85 to 87.

In each of the following tables which demonstrate the effect of thefactors referred to above, the moisture content of the starch beforetreatment with aluminum chloride was adjusted without resort to heat. Inthe cases of the 20 percent, 15 percent, and 10 percent moisture values,the moisture content of the starch was adjusted by air drying the sameat room temperature. In the case of the 5 percent moisture value, theadiustment was made by drying the starch over sulfuric acid. In eachinstance the starch underchloride was added ,'.by the slurry methodpreviously described. Where pH. values are given these were determinedas of the slurry before filtering and drying the starch. Themoisturecontent of the starch was maintained throughout the treatmentsubstantially at the values indicated in the tables.

Table I demonstrates the influence of moisture content upon the rate ofmodification of starch withaluminum chloride at several time intervals.The heat treatment was effected in an oven at a temperature of 100 C.The amount of aluminum chloride used was 0.1 percent, based upon the dryweight of the starch. The results are expressed in terms of solutionviscosity.

Table I [0.1% of Alm -611:0; pH value-=32; 100 0.]

57 Mois- 10" Mois- 157 Mois- 20 Mois- Time, Min. turc lum ture ture inuxinux UIDXIO "IIDXIO 5. 52 14. 33 14. 28 1e. 05 4. 13. :30 14. 41 15.683. 20 11.12 14. 91 1s. 55 0.83 3. 5s 9. 02 a 91 0. 44 2.15 5.50 3.97 0.19 0. 44 0. 4e 0. 55

Table II also demonstrates the effect of moisture content on starchtreated with aluminum chloride for varying periods of time. The amountof aluminum chloride used was 0.1 percent based upon the dry weight ofthe starch and the temperature of the oven used to effect the treatmentwas 100 C. The results are expressed in terms of the percent of solublematerial formed.

Table I! [0.1% of Alm -(EH10; pH value=3.2; 100 (1.]

9% 15% 0% Time Min Moisture Moisture Moisture Moisture Percent PercentPercent Percent Soluble Soluble Soluble Soluble Table III compares theamount of soluble material formed at different levels of solutionviscosity when starch is modified with aluminum chloride. The amount ofaluminum chloride used was 0.1 percent based upon the dry weight of thestarch and the temperature of the oven going treatment was raw cornstarch. The in which treatment was effected was 100 C.

Table III [0.1% of AlClg-fiHgO; pH value-3.2; 100 C.]

5% Moisture 10% Moisture 15% Moisture 20% Moisture mmxm Pcggint mmxloPesrglent flwxm Peggfnt ,mxm Plgglent aeoaoss Table IV demonstrates theelect of temperature on the rate of modification of starch containing 5percent moisture when modified with 0.1 percent of aluminum chloridebased upon the dry weight of the starch. The heat treatment waseflfected in an oven at 100 0., 75 0., and 50' C. The results areexpressed in terms of solution viscosity.

Table IV [5% moisture; 0.1% of AlCh-6H|0; pH value-3.2.]

100 C 75 0. 50 C a x 10 10X 10 a. x10

Table V demonstrates the effect at 100 C. (oven temperature) ofdifferent amounts of aluminum chloride on starch having a moisturecontent of 5 percent for varying intervals of time. The amounts ofaluminum chloride used were 0.1 percent and 0.2 percent, each based uponthe dry weight of the starch. The results are expressed in terms ofpercentage of soluble material, reducing value expressed as ferricyanidenumber, the percentage of linear material and solution viscosity.

Table V [0.1 Alclyefigo pH va1ue= 3.45; 100' 0.;

5 moisture] Per cent Ferricyanide Per cent Soluble No. Linear X [0.2AlCl -6H 0; pH value=3.45 100 C. 5% moisture] Per cent Ferricyanlde Percent Tune Soluble -No. Linear Table VI demonstrates the effect ofseveral methods of adding aluminum chloride to starch to be treated inthe presence thereof. Aluminum chloride was added to starch by theslurry method, by blending with dry starch and in alcoholic solution. Ineach case the amount of aluminum chloride present with the starch duringheat treatment was 0.1 percent, based upon the dry weight of the starch.The moisture content was 5 percent and the temperature of the oven inwhich treatment was effected was 100" C. The

results are expressed in terms of solution viscosity.

Table VI [5% moisture; 0.1% of Alma-611 0; 0.]

Slurry Alcoholic Time, Min. Method Dry Blend Solution flop X10 qI XIO qX10 Most natural starches are now considered to be mixtures of two typesof polymers; one is essentially linear in molecular configuration and isgenerally referred to as amylose; and the other, the major portion,ishighly branched in molecular configuration and is generally referredto as anrylopectin. The linear chain polymers impart to starch pastestheir gel forming properties while the branched chain polymers impart tostarch pastes their protective colloidal and adhesive characteristics.

Hydrolysis of starch tends to break down both components of the starchin random fashion to produce fragments of lower molecular weight withconsequent increase in the reducing value of the hydrolysate. Also ashydrolysis of starch proceeds an increase in solubility and a decreasein viscosity are noted. The end product of hydrolysis of starch isdextrose while at various in- Condensation, on the other hand, as theterm is herein employed is intended to refer to a phenomenon which isthe opposite of hydrolysis as above described, and is intended to relateto chemical changes occurring in respect of the products of the initialphases of hydrolysis of starch. Aluminum chloride being acidic incharacter catalyzes the hydrolysis of starch but under the conditionsessential to the practice of the present invention condensation effectsare materially enhanced over those observed as an incident to theconventional hydrolysis of starch as catalyzed, for example, byhydrochloric acid.

Condensation involves the elimination of water by the formation ofglycosidic linkages either interor intramolecular. In the case of theformation of intermolecular glycosidic linkages, the relative molecularweight of the resulting condensates is increased. In the case of theformation of intramolecular linkages, the molecular weight is notincreased but the shape factors of the resulting molecules are sochanged that some of the characteristics associated with linearity areeliminated and those characteristics associated with the branched chaincomponent correspondingly enhanced. The latter effect may be noted alsoin the case of the formation of intermolecular glycosidic linkagesinthose instances in which condensation results in the formation ofbranched chain molecules, thus again en- 11 harming the characteristicsassociated with the branched chain component of starch. The net effectof condensation is to increase the characteristics associated with thenon-linear components of starch. Condensation brings about a decrease inreducing value and an increase in water solubility. The soluble materialformed upon condensation is of a different character than that formedupon hydrolysis of starch. The soluble material formed upon condensationappears to be composed of branched chain polymers formed fromcondensation of the linear polymers. Pastes made from the products ofcondensation are stable on standing and do not form insoluble gels andhave a relatively high viscosity as compared to starches which have beenhydrolyzed or modified with hydrochloric acid.

The modification of starch inaccordance with the present invention ischaracterized by the relatively great extent to which condensationoccurs and by the relatively great extent to which the eflects ofcondensation characterize the resultant products as compared withprocesses and pH value was 3.45, in the second, 3.45 and in the.

third, 1.9. The moisture content of the starch was 5 percent and thetemperature of the oven wherein the treatment was effected was 100 C.The results are expressed in terms of solution viscosity.

Table VII [5% moisture; 100 0.]

H01 at equiv. H01 at equiv. Time, H ion concn. chloride ion concn. Min.P X10 pH value=3.45 pH value=l.9

mp 10x inux 0 Table VIII compares the effect on starch of aluminumchloride and hydrochloric acid at an equivalent chloride ionconcentration at two moisture values, 5 percent and 20 percent. The

amount of aluminum chloride used was 0.1 percent based upon the dryweight of the starch; the pH value was 3.2.- The pH value in the case ofthe hydrochloric acid and starch containing 5 percent of moisture was1.9; for hydrochloric acid and starch containing 20 percent of moistureit was 2.5. The temperature of the oven in which the treatment waseffected was 100 C. The results are expressed in terms of solublematerial and ferricyanide number.

Table VIII [AlClz-GHrO pH va1ue=3.2; l00 0.]

5% Moisture 20% Moisture Per Cent Ferricyanide Per Cent FerricyunidcSolubles N o. Solubles o pH Value=l.9 pH Va1ue=2.5 5% Moisture 20%Moisture Per Cent Fcrricyanidc Per Cent Ferricyanide Solubles No.Solubles N o.

Table IX compares the amount of linear polymers and the reducing valuesof starches treated with 0.1 percent of aluminum chloride (dry basis)and hydrochloric acid at a chloride ion concentration equivalent to thatobtained with the aluminum chloride. In the former case the pH value was3.45 while in the latter it was 1.9. The moisture content of the starchwas 5%. The temperature of the oven in which treatment was carried outwas 100 C. The time in minutes is also given.

Table IX [5% moisture; 100 0.]

AlClrfiHzO- DH value=3A5 H(lpH mint-1.0

Time, Min.

if g g Ferricyanide l errie vanide Polymers Polymers Table X comparesfluidity values, Stormer values of cold pastes, and gel strength of coldpastes made from corn starch modified in the presence of aluminumchloride and a commercial corn It will be noted from the above tablesthat starches treated in accordance with the present invention diii'erconsiderably in properties from acid modified starches. Thus for a givenviscosity and for a given solubility value, the reducing value of starchmodified in the presence of aluminum chloride is considerably less thanfor an acid modified starch. For a given viscosity, the content of watersoluble material is higher for starch modified with aluminum chloridethan for starch modified with hydrochloric acid. Pastes made from starchmodified with aluminum chloride have much less tendency to increase inviscosity on aging or to become insoluble on aging than do pastes madefrom raw or acid modified starches. Furthermore, the gel strength ofpaste made from starch treated in accordance with the present inventionis much less than that of paste made from other modified starches havingcomparable hot paste viscosities.

starches modified with aluminum chloride have superior protectivecolloidal properties as compared to acid modified starches.Consequently, the former are extremely valuable in applicationsdepending upon colloidal properties of starch, e. g., applications inwhich they are used as carriers, adhesives, sizes and the like.

The following examples, which are intended as informative and typicalonly and not in a limiting sense, will further illustrate the invention,which is intended to be limited only in accordance with the scope of theappended claims.

Thin-boiling starches from starch by modification with aluminum chlorideExample 1.Crn starch from the second American filters in the wet millingof corn was slurried in condensate water (from boilers and processevaporators) at a concentration corresponding to 20 B. (corrected to 60F'.). The pH value of the slurry at this point was about 4.1. A watersolution of aluminum chloride was then added with stirring so that themixture contained 2 lbs. of A1C1a-6H2O for every 1000 lbs. of starch,dry substance. The pH value of the slurry was then 3.0. The slurry wasfiltered'on a continuous suction filter, reducing the moisture contentto 44-46%.

The cake discharge from the filter was passed over a breaker to reducethe cake particle size,

and the broken cake was dropped onto an endless belt which carried themoist cake through a series of heated chambers, and then into a coolingchamber. During passage, the moisture content oi the starch was reducedto about 10% in 30 to 45 minutes total time. The starch was finallypassed into a neutralizing and blending chamber where, by theintroduction of gaseous ammonia, the pH value of the starch was adjustedinstantaneously to about 5 to 6.

A filter of the Oliver type was used to supply the cake to a belt drierof the Proctor-Schwart type (Model K 3514) It was found advantageous tolimit the thickness of the filter cake to 0.25 to 0.50 inch and to breakthese sheets into pieces about 1 x 2 inches.

The drier consisted of six sections with forced draft through each. Theair temperature in th sections was limited as follows: 1

Section 1, 120 F. (starch temperature about 100 F.) Section 2, 150 F.Section 3, 200-215 F. Section 4, 225-235" F. Section 5, 235-245 F.Section 6, 245-255 l (starch temperature about Air was passed throughthe drier at the rate of 14,700 cu. ft. per minute. Tests at the inlet.

1. e., to section 1 and at the exhaust, i. e., from section 6 show:'

Inlet Exhaust Dry bulb temperature F 81' 154 Wet bulb temperature ..F..71 117 Relative humidity percent-. 62 33 Lbs. water/lb. air 0. 014 0.056

' so as to lay a 2 inch bed of broken cake at 45% moisture on the drierbelt, the starchemerged at 10.5% moisture. The fluidity value of thestarch so treated was 50.

Example 2.When the delivery of the starch (as in Example 1) from thefilter to the drier was reduced so that a bed of cake 1% inches in depthwas deposited, the final moisture in the starch was 8% and the fluidityvalue was 65.

Example 3.When 0.4% AlCb-GHzO, based upon the dry weight of the starch,was added to the starch slurry which had a pH value of 2.9, a 2 inch bedof cake at 45% moisture deposited on the belt and passed in 30 minutesthrough the chambers, the air temperature of which were Section 1, 135F. (starch temperature about 100 F.)

Section 2, 230 F.

Section 3, 250 F.

Section 4, 260 F.

Section 5, 270 F.

Section 6, 280 -F'. (starch temperature about the starch after coolingemerged at 10% moisture content and had a fluidity value of 90.

Example 4.-Whe'n 0.2 AlCls-6H2O, based upon the dry weight of thestarch, was added to the starch slurry and a 1 inch bed of cake at 45%moisture was deposited on the belt moving through chambers as in Example3, the product emerged at 5-6% moisture and gave a fluidity value of 80.

Dextrins from starch by modification with aluminum chloride samplewastaken, neutralized with ammonia and inspected. Its paste viscositywas entirely too high to be considered as a dextrin. A sample wastaken'after 75 minutes of heating when the temperature had reached 212F. The product now had a moisture content of 6.5%, contained 27.9% coldwater solubles and produced a fiuid .paste when theproduct was cooked ina 25% concentration with water. At this point the characteristics of thetreated starch were such as to make it suitable for use as a gum in claycoating paper. When the temperature had reached 220 F. at the end ofanother 15 minutes of heating, the

paste consistency of the dextrin was reduced to such an extent that itwas suitable for use as a seam and box lining glue, with the addedadvantage that it did not increase in viscosity on standing.

Apparently the dextrinization'proceeds rather slowly at temperaturesbelow 194 F. and thereafter proceeds rapidly.

The process for dextrinization may be made continuous by using a chamberpreheated to 220 F. and of proper design for moving the starch from oneend to the other over a 15 minute period.

Cold water dispersible roll-treated products involving modification ofstarch by aluminum chloride Example 6.Corn starch, as in Example 1, wasmade up to B. slurry in water and 0.075% AICh'GHZO, based on the dryweight of the starch, was added. The pH value of the slurry was about3.4. After filtration the cake containing 45% moisture was fed to thevalley between a set of heated double rolls, inches in diameter,operating at 5 R. P. M. and heated with 160 lbs. stream pressure. Theresulting gelatinized, modified, and dried product was cooled, ground,and bolted. It was completely dispersible in cold water, contained 20 tocold water soluble material and possessed excellent colloidal propertiesfor retention of water in and maintaining the viscosity of oil welldrilling muds.

Example ?.Corn starch, as in Example 1, was made up to 23 B.concentration in water and 0.125% AlCl3-6H2O, based on the dry weight ofthe starch, was added. This slurry (pH value of 3.4) was fed directly toheated rolls (as in Example 6), operated at 8 R. P. M. The product fromthe rolls was cooled, ground, bolted, and adjusted to a pH value of 6 byexposure to ammonia.

This product, which contained 70-35% cold water soluble material,exhibited excellent sizing properties.

Example 8.--Corn starch, as in Example 1, was made up to 23 B.concentration in water and 0.3% A1C13'6H2O, based upon the dry weight ofthe starch, was added. This slurry (pH value of 3.2) was fed to rolls asin Example 7. The product, thoroughly and quickly cooled to 80 F. orbelow as it left the rolls, was ground, bolted and adjusted to a pHvalue of 5 to 6 by exposure to ammonia.

This product was 98-l00% cold water soluble. It mixed readily with anequal weight of water to form a fluid glue, the consistency of whichremained practically constant for extended periods of time whenprecaution was taken against evaporation and possible microbiologicalaction.

Treatment of starches other than corn starch with aluminum chlorideExample 9.--Slurries of tapioca, rice, corn, and potato tarches weremade, using, by weight, 100 parts of starch and 163 parts of water. Toeach was added 0.2% A1C1s'6H2O, based upon the dry weight of the starch,and the pH value of each slurry adjusted to 3.1 with hydrochloric acid..

Table XI Moisture of Moisture of Wet Cake, Dried Starch, igg g of PerCent Per Cent Potato starch 43. 7 4. 40 6. 5 Rice starch 45. l 5. 78 15.0 Corn starch. 45. 5 6. 64 66. 0 Tapioca starch... 47. 7 5.02 77. 0

The process of the present invention may be carried out by means of anyof the common types of equipment commercially available for making thinboiling starches, pyrodextrins and pregelati nized starches. The processis simple, economical, and the time required to produce the desiredproducts is considerably less than that required to produce the formerlyknown thin boiling starches, pyrodextrins, pregelatinized starches andthe like.

The principles of the present invention are applicable to variousstarches, e. g-., corn, wheat, rice, tapioca, potato and the like,either in raw or gelatinized state.

I claim:

1. The process of modifying starch which comprises contacting starchwith aluminum chloride hexahydrate at starch temperatures between about20 C. and about 105 0., said aluminum chloride hexahydrate ranging inamount from about 0.05 percent to about 0.5 percent, based upon the dryweight of the starch, said starch undergoing modification containingmoisture ranging in amount from about 1-2 percent to about 20 percent ofthe total weight of starch and moisture, the pH value of said starchundergoing modification ranging from about 2.8 to about 3.4.

2. The process of modifying starch to render it thin boiling whichcomprises contacting starch with aluminum chloride hexahydrate at starchtemperatures of about C. to about C., said aluminum chloride hexahydrateranging in amount from about 0.05 percent to about 0.5 percent, basedupon the dryweight of the starch, said starch undergoing treatmentcontaining moisture in the amount of about 9 to about 12 percent of thetotal weight of starch and moisture, the pH value of said starchundergoing modification ranging from about 2.8 to about 3.4.

3. The process according to claim 2 wherein the contact time is of theorder of about 30 minutes.

4. The process of modifying starch to produce pyrodextrin whichcomprises contacting starch with aluminum chloride hexahydrate at starchtemperatures of about 90 C. to about C., said aluminum chloridehexahydrate ranging in amount from about 0.05 percent to about 0.5percent, based upon the dry weight of the starch, said starch undergoingtreatment containing moisture in the amount of about 5 to about 7percent of the total weight of starch and mois-' ture, the pH value ofsaid starch undergoing 5. The process according to claim 4 wherein thecontact time is of the order of about to 30 minutes.

6. The process of treating starch contained in mixtures of starch andmoisture wherein the weight of moisture exceeds 30 percent of the totalweight of the starch and moisture which comprises reducing the moisturecontent of the mixture to between about 1 percent and about 30 percentof the total weight of starch and moisture, and thereafter modifying thestarch by contacting the same with aluminum chloride hexahydrate inamounts ranging from about 0.05 percent to about 0.5 percent, based uponthe dry weight of the starch, at a starch temperature between about C.and about 105 C. for a period of time to effect desired modification ofthe starch, the pH value of said starch undergoing modification rangingfrom about 2.8 to about 3.4.

7. The process according to claim 1 wherein said starch is corn starch.

8. The process according to claim 1 wherein said starch is tapiocastarch.

9. The process according to claim 1. wherein said starch is rice starch.

10. The process according to claim 1 in which the modification of thestarch is arrested by treating the modified starch product with analkaline agent in amount to adjust the pH value to at least 5.0.

11. The process according to claim 2 in .which the modification of thestarch is arrested by treating the modified starch product with gaseousammonia to adjust the pH value to at least 5.0.

12. The process according to claim 4 in which the modification of thestarch is arrested by treating the pyrodextrin with gaseous ammonia toadjust the pH value to at least 5.0.

13. The process according to claim 2 wherein said starch is corn starch.

14. The process according to claim 4 wherein said starch is corn starch.

15. A process of treating starch containing mixtures of starch andmoisture wherein the weight of moisture exceeds about 30 percent of thetotal weight of the starch and moisture, which comprises contacting thestarch with aluminum chloride hexahydrate in amounts ranging from about0.05 percent to about 0.5 percent based upon the dry weight of thestarch, reducing the moisture content of the mixture to between about 1percent and about 30 percent of the total weight of starch and moisturewithout effecting modification of the starch, and thereafter modifyingthe starch by maintaining a starch temperature between about 20 C. andabout 105 C.

for a period of time suflicient to effect desired modification of thestarch, the pH value of said starch undergoing modification ranging fromabout 2.8 to about 3.4.

16. A process of treating starch contained in mixtures of starch andmoisture wherein the weight of moisture exceeds about 30 percent of thetotal weight of the starch and moisture, which comprises contacting thestarch with aluminum chloride hexahydrate in amounts ranging from about0.05 percent to about 0.5 percent based upon the dry weight of thestarch, and subjecting the mixture to pressure for a short interval oftime between surfaces maintained at a temperature at about 180 C. whilepermitting free evaporation of moisture, the pH value in said starchundergoing treatment ranging from about 2.8 to about 8.4.

17. The process of treating corn starch which comprises mechanicallydewatering a corn starch slurry containing 0.2 percent of aluminumchloride hexahydrate, based upon the starch dry substance, graduallydecreasing the moisture content of the starch to about 10 percent byheat treatment within a period of about 40 minutes without gelatinizingthe starch, the temperature of the starch not exceeding about 180 F.during said heat treatment, and then heating the starch for about 15minutes in a chamber preheated to and maintained at a temperature ofabout 220 m, and thereafter adjusting the pH value of the starch toabout 5 to 6 by means of gaseous ammonia; the pH value of said starchslurry being about 3.0.

18. The process of treating starch which comprises mechanicallydewatering a starch slurry containing aluminum chloride hexahydrate,gradually decreasing the moisture content of the starch by heattreatment to about 5 to 7 percent without gelatinizing the starch, thetemperature of the starch not exceeding about 180 F. to 200 F. andthereafter adjusting the pH value of the starch to about 5 to 6; saidaluminum chloride hexahydrate being present in said slurry to the extentof about 0.05 percent to 0.5 percent, based upon the starch drysubstance, said slurry having a pH value of about 2.8 to 3.4.

19. The process of treating starch which comprises mechanicallydewatering a starch slurry containing about 0.05 percent to about 0.5percent of aluminum chloride hexahydrate, based upon the dry weight ofthe starch, and having a pH value of 2.8 to 3.4 and subjecting thedewatered starch to heat treatment for about 30 to about 40 minutes togradually decrease the moisture content of the starch to about 10percent without gelatinizing the starch, the temperature of the starchundergoing heat treatment not exceeding about 180 F. to 200 F. andthereafter adjusting the pH value of the starch to 5 to 6.

20. The process of treating corn starch which comprises mechanicallydewatering a corn starch slurry containing about 0.4 percent of aluminumchloride hexahydrate, based upon the dry weight of the starch, having apH value of about 2.9 and a temperature of about F. to F., thensubjecting the dewatered starch to heat treatment for about 30 minutesto gradually decrease the moisture content of the starch to about 10percent without gelatinizing the starch, the temperature of the starchundergoing heat treatment not exceeding about 200 F. and thereafteradjusting the pH value of the starch to 5 to 6.

21. The process according to claim 6 wherein said starch is corn starch.

22. The process according to claim 16 wherein said starch is cornstarch.

23. The process according to claim 18 wherein said starch is cornstarch.

24. The process according to claim 19 wherein said starch is cornstarch.

25. The method according to claim 6 wherein the modification of thestarch is arrested by treating it with an alkaline agent to adjust thepH value to at least about 5.0.

RALPH WALDO KERR.

(References on following page) summons 20 REFERENCES CITED Number NameDate The followin ref rences are of record in the 1616'165 Arsem 1927file of this paxb ent: 8 1,942,544 Fuller Jan. 9, 1934 UNITED STATESPATENTS 6 b S f PATENTS te um er oun ry Da Number Name Date 536,260Bloede Mar. 26, 1895 25,121 Great Britain 1909 610,182 Higgins Sept. 6,1898 OTHER REFERENCES 773,469 Browning et a1 Oct. 25, 1904 h 1,284,495Tunnel] Nov. 12, 1 19 err. chem. and Ind. 01' Starch, N. Y. 1944,

pages 54-56.

1. THE PROCESS OF MODIFYING STARCH WHICH COMPRISES CONTACTING STARCHWITH ALUMINUM CHLORIDE HEXAHYDRATE AT STARCH TEMPERATURES BETWEEN ABOUT20*C. AND ABOUT 105*C., SAID ALUMINUM CHLORIDE HEXAHYDRATE RANGING INAMOUNT FROM ABOUT 0.05 PERCENT TO ABOUT 0.5 PERCENT, BASED UPON THE DRYWEIGHT OF THE STARCH, SAID STARCH UNDERGOING MODIFICATION CONTAININGMOISTURE RANGING IN AMOUNT FROM ABOUT 1-2 PERCENT TO ABOUT 20 PERCENT OFTHE TOTAL WEIGHT OF STARCH AND MOISTURE, THE PH VALVE OF SAID STARCHUNDERGOING MODIFICATION RANGING FROM ABOUT 2.8 TO ABOUT 3.4.